I have purchased an encoder which has open collector and 3.3 Kohm pull-up resistor (TTL) as its logic output.The encoder comes with four leads: +5V power, GND, Channel A and Channel B. Both Channel A and Channel B are logic output. Channel A and Channel B are connected to the DIO of NI-9401 which is mounted on cRIO.A standard VI for encoder counting is used and compiled under the FPGA environment. During the measurement, I observed that there are significant loss count in both encoder direction.I do not think that there is any problem with the VI as I have used it quite a few times on encoders with RS422 logic output. Is there any problem with my current encoder in terms of its electrical interface with NI-9401? Thanks.

I do not think that there is a problem with the pull-up resistor. Even if the digital i/o ports have their own pull-up resistors (usually in the range of 4.7kOhm - should be specified in the manual), the current to be handled by the output transistor of the encoder circuitry is about 2mA. - Check your setup for proper GND connection. You should connect GND of the encoder power supply directly to the DGND terminal of the pc board.

Digital I/O

Encoder interfaced with NI-9401

Solved!

I had earlier the same problems, but solved them. I see that going through exactly the same path as me.

You have to do it like this:

1. Forward FXP to RT and only there do the conversion.

2. I set empirically by means of measuring the speed and chose this value. It depends on the sensor.

3. If you have measured the speed, now you control the output voltage of a power supply. I used to use the old low voltage power supply controllable, and he zwielokratniał them (in 9263, I lived cards). Anyway, you need to have the card outputs AO.

4. I don't known

Also:

1. You must click right mouse button in project on Build Specifications>>Real-Time Application

2. https://forums.ni.com/t5/LabVIEW/crio-standalone/td-p/2337256